Drier with straight and sawtooth lifters



March 20, 1962 I I M. B. FREEMAN 3,025,611

DRIER WITH STRAIGHT AND SAWTOOTH LIFTERS' Filed March 24, 1959 /N\//VTOR.

MHRV/N B. /PEEMFIN BY HIS HTTORNEYS. Ha RQ/} MEG/15 PUSSELLG: KER/v The present invention relates in general to a drier for flowable solid materials and since the invention has been embodied in and is particularly applicable to an apparatus for heating and drying the aggregate or aggregates utilized in aggregate-asphalt mixtures, it will be considered in such connection herein for convenience.

In general, the invention contemplates an aggregate drier which includes a generally cylindrical shell mounted for rotation about its longitudinal axis with such axis inclined downwardly from the inlet end of the shell to the outlet end thereof so that the aggregates being dried and heated progress from the inlet end of the shell to the outlet end thereof under the influence of gravity as the shell is rotated about its longitudinal axis. Lifter plates are provided within the shell for lifting the aggregates and dropping them through a stream of hot gaseous fluid flowing longitudinally of the shell, such lifter plates operating in response to rotation of the shell. The hot gaseous fluid may be hot air, hot products of combustion of a suitable fuel in air, or the like, the flow of hot gaseous fluid longitudinally of the shell and the flow of aggregates longitudinally thereof being countercurrent. In other words, the stream of hot gaseous fluid flows from the outlet end of the shell to the inlet end thereof.

A primary object of the invention is to provide a drier of the foregoing nature wherein the lifter plates or lifters are so constructed and arranged that adequate draft for the hot gaseous fluid is maintained to prevent plugging of the drier.

More particularly, an important object of the invention is to provide a drier wherein the lifters adjacent the inlet or feed end of the shell have straight discharge edges and wherein the lifters adjacent the outlet or discharge end of the shell have serrated or sawtooth discharge edges.

With the foregoing construction, the wetter material being handled adjacent the inlet end of the shell, which wetter material tends to offer more draft resistance, is caused to fall downwardly from the straight lifter plates in relatively thin sheets to minimize the draft resistance in the wet end of the shell. Adjacent the outlet or dry end of the shell, however, the dried, or partially dried, material being handled offers less draft resistance and, in this region, the sawtooth lifters or lifter plates cause the aggregates to rain" downwardly in relatively thick sheets or streams to obtain more intimate contact between the aggregates and the hot gaseous fluid.

Thus, the present invention reduces draft resistance adjacent the inlet or wet end of the shell, where the water content of the aggregates tends to produce maximum draft resistance, by employing straight lifter plates to minimize the obstruction to the flow of the hot gaseous fluid. On the other hand, adjacent the outlet or dry end of the shell, where the water content of the aggregates is reduced to reduce draft resistance, the invention provides sawtooth lifters to obtain more intimate contact between the aggregates and the hot gaseous fluid for more effective heating and drying.

Another object of the invention is to provide straight lifters or lifter plates having outer portions substantially perpendicular to the circumferential wall of the shell and extending radially inwardly therefrom, and inner portions which project generally circumferentially of the shell in the direction of rotation of the shell and which terminate in straight inner edges. A related object is to provide straight lifters which are channel-shaped in cross section and which face in the direction of rotation of the shell.

Another object is to provide sawtooth lifters or lifter plates which include outer portions substantially perpendicular to the circumferential wall of the shell and extending radially inwardly therefrom, intermediate portions which project inwardly and circumferentially of the shell in the direction of rotation of the shell, and inner portions which project generally circumferentially of the shell in the direction of rotation of the shell, such inner portions terminating in serrated inner edges.

A further object of the invention is to provide a drier wherein the sawtooth lifters and the straight or channel lifters are circumferentially staggered relative to each other.

Still another object is to provide a drier wherein the sawtooth lifters are divided into two groups one adjacent the outlet end of the shell and the other intermediate the first group and the straight or channel lifters, the sawtooth lifters of such other group being staggered circumferentially relative to the sawtooth lifters of the first group and relative to the straight or channel lifters.

The foregoing circumferential staggering of the straight or channel lifters and the two groups of sawtooth lifters has the effect of achieving more intimate contact between the aggregates and the hot gaseous stream.

The foregoing objects, advantages, features and results of the present invention, together with various other objects, advantages, features and results thereof which will be evident to those skilled in the drier art in the light of this disclosure, may be attained with the exemplary embodiment of the invention described in detail hereinafter and illustrated in the accompanying drawing, in which:

FIG. 1 is a side elevational view of a drier which embodies the invention;

FIG. 2 is an enlarged, fragmentary sectional view taken along the arrowed line 22 of FIG. 1;

FIG. 3 is a fragmentary sectional view taken along the arrowed line 33 of FIG. 2; and

FIG. 4 is a fragmentary sectional view taken along the arrowed line 44 of FIG. 3.

In the drawing, the numeral 10 designates a frame on which is mounted an aggregate drier 12 comprising a generally cylindrical shell 14 having an inlet or feed end 16 and an outlet or discharge end 13. The shell 14 is rotatable about its longitudinal axis and slopes downwardly from its inlet end 16 to its outlet end 18 so that material being heated and dried moves from the inlet end of the shell to the outlet end thereof by gravity in response to rotation of the shell.

The shell 14 may be mounted for rotation in the foregoing manner in any suitable manner, as by providing it with circumferential rails 24} which engage flanged rollers 22 on the frame It The shell 14 carries a ring gear 24- meshed with a driving gear 26 rotatably mounted on the frame 10, whereby to rotate the shell about its longitudinal axis.

The drier 12 may be supplied with aggregates, or other material, to be dried by a bucket conveyor 23 discharging into an inlet hopper 3th in communication with the inlet end 16 of the shell 14, although the drier may be supplied in other ways also. The outlet end 18 of the shell 14 communicates with a discharge means 32 of any suitable construction, the aggregates dried within the shell 14 leaving the drier 12 by way of such discharge means.

A heating means 34, supplied with air by a blower 36, communicates with the outlet end 18 of the shell 14, the stream of hot gaseous fluid produced by the heating means and the blower being discharged from the inlet end 16 of the shell through an exhaust means 38 communicating therewith. The exhaust means 38 communicates with a stack 40 which may lead to any suitable point of disposal of dust, and the like.

It will be noted that the flow of aggregates and the flow of the hot gaseous fluid are countercurrent, the aggregates flowing downwardly from the inlet end 16 to the outlet end 18 of the shell 14, and the hot gaseous stream flowing upwardly through the shell from the outlet end 18 of the shell to the inlet end 16 thereof. Thus, the nearly dried aggregates adjacent the outlet end 18 of the shell 14 are exposed to the hottest portion of the gaseous stream to achieve final drying thereof.

The shell 14 carries internally thereof circumferentially spaced, longitudinally extending straight lifters 42 adjacent its inlet end 16 and circumferentially spaced, longitudinally extending sawtooth lifters 44 and 46 adjacent its outlet end 18, the sawtooth lifters 44 being disposed between the straight lifters 42 and the sawtooth lifters 46. The sawtooth lifters 44 are staggered circumferentially relative to the straight lifters 42 and the sawtooth lifters 46 are staggered circumferentially relative to the sawtooth lifters 44 for the reason hereinbefore indicated.

Each straight lifter or lifter plate 42 comprises an outer portion 48 which is substantially perpendicular to the circumferential wall of the shell 14 and which extends radially inwardly therefrom, and an inner portion 50 which projects generally circumferentially of the shell from the outer portion 46 in the direction of rotation 64 of the shell about its longitudinal axis. The inner portions 50- of the straight lifters 42 terminate in straight inner edges 52.

In the construction illustrated, each straight lifter 42 is channel-shaped in cross section and is mounted on one or more brackets 54 suitably secured to the shell 14. The outer portion 48 of each straight lifter 42 is formed by the web and one of the flanges of the corresponding channel, and the inner portion 50 thereof is formed by the other flange of the channel.

Each of the sawtooth lifters 44 and 46 includes an outer, substantially radial, inwardly projecting portion 58 which is secured to one or more brackets 60 on the inner surface of the circumferential wall of the shell 14. Each of the sawtooth lifters 44 and 46 also includes an intermediate portion 62 which projects inwardly and circumferentially of the shell from the outer portion 58 in the direction of rotation of the shell, the direction of rotation being designated by the arrow 64. In order to achieve optimum aggregate capacity for each of the lifters 44 and 46, the intermediate portion 62 thereof preferably makes an angle of approximately with the shell 14. Each of the sawtooth lifters 44 and 46 further includes an inner portion 66 which projects generally circumferentially of, and slightly inwardly of, the shell 14 from the corresponding intermediate portion 62 in the direction of rotation of the shell. Each inner portion 66 terminates in an iner edge 67 which is serrated to provide teeth 68 spaced apart longitudinally of the corresponding lifter plate, the inner edge of each inner portion 66 being serrated substantially to the intermediate portion 62 of the corresponding lifter or lifter plate.

Since the outer portions 58 of the sawtooth lifters 44 and 46 are generally perpendicular to the shell 14, packing of wet material in the corners formed by these lifters and the shell is minimized as opposed to a construction wherein the lifters and the shell make acute angles.

Considering the operation of the invention, it will be seen that, as the shell 14 rotates, the lifters 42, 44 and 46 act as buckets and scoop up the aggregates being heated and dried, the lifters carrying the aggregates upwardly. Continued rotation of the shell 14 first causes the buckets formed by the lifters to turn on their sides, and then invert, the aggregates being dumped therefrom as this takes place.

The straight lifters 42 distribute the falling aggregates, which are relatively wet adjacent the inlet end 16 of the shell 14, in relatively thin streams. Such streams minimize the draft resistance provided by the relatively wet aggregates adjacent the wet or inlet end 16 of the shell 14 to provide maximum draft in this region.

On the other hand, the sawtooth lifters 44 and 46 distribute the relatively dry aggregates adjacent the dry or outlet end 18 of the shell 14 in relatively wide streams having large horizontal cross sectional areas, this being due to the fact that the aggregates fall off all portions of the edges of the teeth 68. Consequently, the aggregates rain downwardly in a substantially uniform pattern throughout the entire hot gaseous stream flowing longitudinally through the shell 14 adjacent the outlet end 18 thereof, thereby obtaining maximum contact between the aggregates and the hot gaseous stream. The drier aggregates adjacent the dry end 18 of the shell 14 do not oifer as much draft resistance as the relatively wet aggregates adjacent the wet end 16 of the shell so that the sawtooth lifters 44 and 46 do not affect draft conditions excessively, while providing the desired intimate contact between the aggregates and the hot gaseous stream.

Thus, the present invention, by utilizing the straight or channel lifters 42 adjacent the wet or inlet end 16 of the shell 14 to minimize draft resistance where the draft resistance tends to be high, and by utilizing the sawtooth lifters 44 and 46 adjacent the dry or outlet end 18 of the shell, where the draft resistance tends to be lower, provides both adequate draft throughout the length of the shell and intimate mixing of the aggregates and the hot gaseous stream to provide efficient drying.

For optimum results, the straight lifters 42 occupy a little less than one-half the length of that portion of the shell 14 which contains the lifters 42, 44 and 46. For example, the straight lifters 42 may occupy a portion of the shell 14 ten feet long and the sawtooth lifters 44 land 46 may each occupy a portion of the shell six feet ong.

Although an exemplary embodiment of the invention has been disclosed herein for purposes of illustration, it will be understood that various changes, modifications and substitutions may be incorporated in such embodiment without departing from the spirit of the invention as defined by the claim which follows.

I claim:

In combination: a frame; a generally cylindrical shell having inlet and outlet ends; means mounting said shell on said frame for rotation about its longitudinal axis, said longitudinal axis sloping downwardly from said inlet end of said shell to said outlet end thereof; means for introducing a material to be dried into said inlet end of said shell; means for circulating a heated gaseous fluid through said shell from said outlet end of said shell to said inlet end thereof; a plurality of straight lifter plates within and mounted on the circumferential wall of said shell adjacent said inlet end thereof, said straight lifter plates being spaced apart circumferentially of said shell and extending longitudinally thereof, each of said straight lifter plates including an outer portion which is substantially perpendicular to said circumferential wall and which extends radially inwardly therefrom and an inner portion which projects generally circumferentially of said shell in the direction of rotation of said shell about said longitudinal axis, said inner portion of each of said straight lifter plates terminating in a straight inner edge; and a plurality of sawtooth lifter plates within and mounted on the circumferential wall of said shell adjacent said outlet end thereof, said sawtooth lifter plates being spaced apart circumferentially of said shell and extending longitudinally thereof, each of said sawtooth lifter plates including an outer portion which is substantially perpendicular to said circumferential wall and which extends radially inwardly therefrom, and including another portion which projects from said outer portion thereof inwardly and circumferentially of said shell in the direction of rotation 5 6 of said shell about said longitudinal axis, said other por- References Cited in the file of this patent tionof said each of said sawteoth lifter pi ates terminat- UNETED STATES PATENTS mg in a serrated lnner edge, sald straight llrter plates and said sawtooth lifter plates extending radially inwardly 7 914,952 Kent Man 1909 from said circumferential Wall of said shell substantially 5 fifigy gj equal distances. 

